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Subject[PATCH 1/1] [GPIO]: new arch-independent simple-gpio driver
Date
From: Mike Frysinger <vapier.adi@gmail.com>

Signed-off-by: Mike Frysinger <vapier.adi@gmail.com>
Signed-off-by: Bryan Wu <cooloney@kernel.org>
---
drivers/char/Kconfig | 14 ++
drivers/char/Makefile | 1 +
drivers/char/simple-gpio.c | 308 ++++++++++++++++++++++++++++++++++++++++++++
3 files changed, 323 insertions(+), 0 deletions(-)
create mode 100644 drivers/char/simple-gpio.c
diff --git a/drivers/char/Kconfig b/drivers/char/Kconfig
index 47c6be8..dd17d06 100644
--- a/drivers/char/Kconfig
+++ b/drivers/char/Kconfig
@@ -4,6 +4,20 @@

menu "Character devices"

+config SIMPLE_GPIO
+ tristate "Simple GPIO char interface"
+ depends on GENERIC_GPIO
+ default n
+ help
+ If you say Y here, you will get support for a character device
+ interface to the GPIO pins which will allow you to read and
+ write GPIO values from userspace.
+
+ To compile this driver as a module, choose M here: the module
+ will be called simple-gpio.
+
+ If unsure, it is safe to say Y.
+
config VT
bool "Virtual terminal" if EMBEDDED
depends on !S390
diff --git a/drivers/char/Makefile b/drivers/char/Makefile
index 5407b76..e087ec1 100644
--- a/drivers/char/Makefile
+++ b/drivers/char/Makefile
@@ -97,6 +97,7 @@ obj-$(CONFIG_CS5535_GPIO) += cs5535_gpio.o
obj-$(CONFIG_GPIO_VR41XX) += vr41xx_giu.o
obj-$(CONFIG_GPIO_TB0219) += tb0219.o
obj-$(CONFIG_TELCLOCK) += tlclk.o
+obj-$(CONFIG_SIMPLE_GPIO) += simple-gpio.o

obj-$(CONFIG_MWAVE) += mwave/
obj-$(CONFIG_AGP) += agp/
diff --git a/drivers/char/simple-gpio.c b/drivers/char/simple-gpio.c
new file mode 100644
index 0000000..36204ca
--- /dev/null
+++ b/drivers/char/simple-gpio.c
@@ -0,0 +1,308 @@
+/*
+ * Simple character interface to GPIOs. Allows you to read/write values and
+ * control the direction. Maybe add wakeup when gpio framework supports it ...
+ *
+ * To use, just declare in your board resources:
+ * static struct resource foo_resources[] = {
+ * .start = 0,
+ * .end = 5,
+ * .flags = IORESOURCE_IRQ,
+ * };
+ * static struct platform_device foo_dev = {
+ * .name = "simple-gpio",
+ * .num_resources = 1,
+ * .resource = &foo_resources
+ * };
+ * This will setup GPIO0 - GPIO5 (inclusive) for use by this driver.
+ *
+ * Copyright 2008 Analog Devices Inc.
+ *
+ * Licensed under the GPL-2 or later.
+ */
+
+#include <linux/cdev.h>
+#include <linux/device.h>
+#include <linux/errno.h>
+#include <linux/fs.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/platform_device.h>
+#include <linux/types.h>
+
+#include <asm/atomic.h>
+#include <asm/gpio.h>
+#include <asm/uaccess.h>
+
+#define stamp(fmt, args...) pr_debug("%s:%i: " fmt "\n", __func__, __LINE__, ## args)
+#define stampit() stamp("here i am")
+#define pr_devinit(fmt, args...) ({ static const __devinitdata char __fmt[] = fmt; printk(__fmt, ## args); })
+#define pr_init(fmt, args...) ({ static const __initdata char __fmt[] = fmt; printk(__fmt, ## args); })
+
+#define DRIVER_NAME "simple-gpio"
+#define PFX DRIVER_NAME ": "
+
+struct gpio_data {
+ atomic_t open_count;
+};
+struct group_data {
+ dev_t dev_node;
+ struct cdev cdev;
+ struct resource *gpio_range;
+ struct gpio_data *gpios;
+};
+
+/**
+ * simple_gpio_read - sample the value of the specified GPIO
+ */
+static ssize_t simple_gpio_read(struct file *file, char __user *buf, size_t count, loff_t *pos)
+{
+ unsigned int gpio = iminor(file->f_path.dentry->d_inode);
+ ssize_t ret;
+
+ stampit();
+
+ for (ret = 0; ret < count; ++ret) {
+ char byte = '0' + gpio_get_value(gpio);
+ if (put_user(byte, buf + ret))
+ break;
+ }
+
+ return ret;
+}
+
+/**
+ * simple_gpio_write - modify the state of the specified GPIO
+ *
+ * We allow people to control the direction and value of the specified GPIO.
+ * You can only change these once per write though. We process the user buf
+ * and only do the last thing specified. We also ignore newlines. This way
+ * you can quickly test by doing from the shell:
+ * $ echo 'O1' > /dev/gpio8
+ * This will set GPIO8 to ouput mode and set the value to 1.
+ */
+static ssize_t simple_gpio_write(struct file *file, const char __user *buf, size_t count, loff_t *pos)
+{
+ unsigned int gpio = iminor(file->f_path.dentry->d_inode);
+ ssize_t ret;
+ char dir = '?', uvalue = '?';
+ int value;
+
+ stampit();
+
+ ret = 0;
+ while (ret < count) {
+ char byte;
+ int user_ret = get_user(byte, buf + ret++);
+ if (user_ret)
+ return user_ret;
+
+ switch (byte) {
+ case '\r':
+ case '\n': continue;
+ case 'I':
+ case 'O': dir = byte; break;
+ case 'T':
+ case '0':
+ case '1': uvalue = byte; break;
+ default: return -EINVAL;
+ }
+ stamp("processed byte '%c'", byte);
+ }
+
+ switch (uvalue) {
+ case '?': value = gpio_get_value(gpio); break;
+ case 'T': value = !gpio_get_value(gpio); break;
+ default: value = uvalue - '0'; break;
+ }
+
+ switch (dir) {
+ case 'I': gpio_direction_input(gpio); break;
+ case 'O': gpio_direction_output(gpio, value); break;
+ }
+
+ if (uvalue != '?')
+ gpio_set_value(gpio, value);
+
+ return ret;
+}
+
+/**
+ * simple_gpio_open - claim the specified GPIO
+ *
+ * Grab the specified GPIO if it's available and keep track of how many times
+ * we've been opened (see close() below). We allow multiple people to open
+ * at the same time as there's no real limitation in the hardware for reading
+ * from different processes. Plus this way you can have one app do the write
+ * and management while quickly monitoring from another by doing:
+ * $ cat /dev/gpio8
+ */
+static int simple_gpio_open(struct inode *ino, struct file *file)
+{
+ struct group_data *group_data = container_of(ino->i_cdev, struct group_data, cdev);
+ unsigned int gpio = iminor(ino);
+ struct gpio_data *gpio_data = &group_data->gpios[gpio - group_data->gpio_range->start];
+ int ret;
+
+ stampit();
+
+ if (gpio < group_data->gpio_range->start || gpio > group_data->gpio_range->end)
+ return -ENXIO;
+
+ ret = gpio_request(gpio, DRIVER_NAME);
+ if (ret)
+ return ret;
+
+ atomic_inc(&gpio_data->open_count);
+
+ return 0;
+}
+
+/**
+ * simple_gpio_close - release the specified GPIO
+ *
+ * Do not actually free the specified GPIO until the last person has closed.
+ * We claim/release here rather than during probe() so that people can swap
+ * between drivers on the fly during runtime without having to load/unload
+ * kernel modules.
+ */
+static int simple_gpio_release(struct inode *ino, struct file *file)
+{
+ struct group_data *group_data = container_of(ino->i_cdev, struct group_data, cdev);
+ unsigned int gpio = iminor(ino);
+ struct gpio_data *gpio_data = &group_data->gpios[gpio - group_data->gpio_range->start];
+
+ stampit();
+
+ /* do not free until last consumer has closed */
+ if (atomic_dec_and_test(&gpio_data->open_count))
+ gpio_free(gpio);
+ else
+ stamp("gpio still in use -- not freeing");
+
+ return 0;
+}
+
+static struct class *simple_gpio_class;
+
+static struct file_operations simple_gpio_fops = {
+ .owner = THIS_MODULE,
+ .read = simple_gpio_read,
+ .write = simple_gpio_write,
+ .open = simple_gpio_open,
+ .release = simple_gpio_release,
+};
+
+/**
+ * simple_gpio_probe - setup the range of GPIOs
+ *
+ * Create a character device for the range of GPIOs and have the minor be
+ * used to specify the GPIO.
+ */
+static int __devinit simple_gpio_probe(struct platform_device *pdev)
+{
+ int ret;
+ struct group_data *group_data;
+ struct resource *gpio_range = platform_get_resource(pdev, IORESOURCE_IRQ, 0);
+ int gpio, gpio_max = gpio_range->end - gpio_range->start + 1;
+
+ stampit();
+
+ group_data = kzalloc(sizeof(*group_data) + sizeof(struct gpio_data) * gpio_max, GFP_KERNEL);
+ if (!group_data)
+ return -ENOMEM;
+ group_data->gpio_range = gpio_range;
+ group_data->gpios = (void *)group_data + sizeof(*group_data);
+ platform_set_drvdata(pdev, group_data);
+
+ ret = alloc_chrdev_region(&group_data->dev_node, gpio_range->start, gpio_max, "gpio");
+ if (ret) {
+ pr_devinit(KERN_ERR PFX "unable to get a char device\n");
+ kfree(group_data);
+ return ret;
+ }
+
+ cdev_init(&group_data->cdev, &simple_gpio_fops);
+ group_data->cdev.owner = THIS_MODULE;
+
+ ret = cdev_add(&group_data->cdev, group_data->dev_node, gpio_max);
+ if (ret) {
+ pr_devinit(KERN_ERR PFX "unable to register char device\n");
+ kfree(group_data);
+ unregister_chrdev_region(group_data->dev_node, gpio_max);
+ return ret;
+ }
+
+ for (gpio = gpio_range->start; gpio < gpio_range->end; ++gpio)
+ device_create(simple_gpio_class, &pdev->dev, group_data->dev_node + gpio, "gpio%i", gpio);
+
+ device_init_wakeup(&pdev->dev, 1);
+
+ pr_devinit(KERN_INFO PFX "now handling %i GPIOs: %i - %i\n",
+ gpio_max, gpio_range->start, gpio_range->end);
+
+ return 0;
+}
+
+/**
+ * simple_gpio_remove - break down the range of GPIOs
+ *
+ * Release the character device and related pieces for this range of GPIOs.
+ */
+static int __devexit simple_gpio_remove(struct platform_device *pdev)
+{
+ struct group_data *group_data = platform_get_drvdata(pdev);
+ struct resource *gpio_range = group_data->gpio_range;
+ int gpio, gpio_max = gpio_range->end - gpio_range->start + 1;
+
+ stampit();
+
+ for (gpio = gpio_range->start; gpio < gpio_range->end; ++gpio)
+ device_destroy(simple_gpio_class, group_data->dev_node + gpio);
+
+ cdev_del(&group_data->cdev);
+ unregister_chrdev_region(group_data->dev_node, gpio_max);
+
+ kfree(group_data);
+
+ return 0;
+}
+
+struct platform_driver simple_gpio_device_driver = {
+ .probe = simple_gpio_probe,
+ .remove = __devexit_p(simple_gpio_remove),
+ .driver = {
+ .name = DRIVER_NAME,
+ }
+};
+
+/**
+ * simple_gpio_init - setup our GPIO device driver
+ *
+ * Create one GPIO class for the entire driver
+ */
+static int __init simple_gpio_init(void)
+{
+ simple_gpio_class = class_create(THIS_MODULE, DRIVER_NAME);
+ if (IS_ERR(simple_gpio_class)) {
+ pr_init(KERN_ERR PFX "unable to create gpio class\n");
+ return PTR_ERR(simple_gpio_class);
+ }
+
+ return platform_driver_register(&simple_gpio_device_driver);
+}
+module_init(simple_gpio_init);
+
+/**
+ * simple_gpio_exit - break down our GPIO device driver
+ */
+static void __exit simple_gpio_exit(void)
+{
+ class_destroy(simple_gpio_class);
+
+ platform_driver_unregister(&simple_gpio_device_driver);
+}
+module_exit(simple_gpio_exit);
+
+MODULE_AUTHOR("Mike Frysinger <vapier@gentoo.org>");
+MODULE_DESCRIPTION("Simple GPIO character interface");
+MODULE_LICENSE("GPL");
--
1.5.4.3

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